1. Field of the Invention
The present invention relates to a golf swing diagnosis system and more particularly to a system of automatically extracting check-point images effective for diagnosing a golfer's swing form with high accuracy.
2. Description of the Related Art
There are proposed various kinds of apparatuses of photographing a golfer's swing, automatically computing information such as the flight distance, orbit, and the like of a hit ball by a computer, and displaying the obtained information for a golfer. These apparatuses allow the golfer to examine the flight distance, orbit, and the like of the hit ball. However, these apparatuses are incapable of providing information useful for improving the golfer's swing form.
In the swing form diagnosis apparatus disclosed in Japanese Patent Application Laid-Open No. 2003-117045, a golfer's swing is photographed to extract images of only specific motion points important for diagnosing the swing form. More specifically, frames regarding the golfer's swing motion are extracted from the golfer's moving image photographed by the photographing means. Specific motion points during the swing motion are judged according to results of analysis of the moving partial images in the differential image between each frame and the reference image. A frame corresponding to each of the specific motion points is extracted to display the image.
An image at an impact time is important for diagnosing the golf swing. The position before the impact time, namely, the take-back and the neighborhood of the switch-over from the top position to the downswing and the position after the impact time are particularly important for diagnosing the golf swing. This is because the swing form cannot be corrected at the impact time, if the golfer has an improper swing in the neighborhood of the impact time. To examine the cause of the improper swing form at the impact time, it is necessary to extract a plurality of images of to-be-checked swing postures from images of the take-back time and in the neighborhood of the top position. Thereby it is possible to diagnose the swing form by taking many to-be-checked points of the swing posture in consideration.
However, in the swing form diagnosis apparatus disclosed in Japanese Patent Application Laid-Open No. 2003-117045, images at the take-back time are extracted by merely executing the differential processing between frames. Thus there is a high possibility that an image of a different position is erroneously extracted for a golfer. An image in which the shaft is horizontal at the take-back time is extracted by regarding the frame having a minimum in the X-direction deviation amount in the result of the differential processing as the frame to be extracted. However, golfers' vertical and horizontal motions during a swing are quite different from each other. Thus in the case of a golfer having a take-back while the golfer is swaying (moves horizontally), a horizontal image of the shaft is extracted at a low degree of accuracy by merely considering the X-direction deviation amount during the take-back.
In the extraction of images at the downswing time and the follow-through time, frames a predetermined period of time before and after the impact-time image which is the reference-point image are extracted. Considering that golfers' swing tempos are quite different from each other, it is impossible to extract an image of the same swing position (swing posture) for a plurality of golfers. Thus even if a golfer intends to improve her/his swing form at the time when the golf club shaft is horizontal by comparing her/his swing form with a swing form of a high-class player or that of a professional player, there is no guarantee that the extracted image of her/his swing form is the image at the time when the golf club shaft is horizontal. Therefore it is impossible to compare her/his swing form with that of the high-class player or that of the professional player in the same swing position (posture).